Electrical protective device



Feb. 21, 1950 c, ox 2,498,120

ELECTRICAL PROTECTIVE DEVICE Filed April 25, 1947 v V I "E NVENTOR CHARLES Aom Fox ATTORNEY Patented Feb. 21, 1950 2,498,120 ELECTRICAL PROTECTIVE DEVICE Charles Adin Fox, Oakland-Village, Mo., assignor to James R. Kearney Corporation,

a corporation oi. Missouri St. Louis,

Application April 25, 1947, Serial No. 743,747

3 Claims. (Cl. 173-324) This invention relates generally to electrical protective devices and more specifically to surge arresters adapted for use in arresting surges resulting from lightning and other causes, the predominant object of the invention being to provide such a protective device with improved shunt means whereby the conductive electrical path extending through the protective device to ground is very greatly improved so that free and unimpeded passage of high frequency surges to ground is provided for.

Fig. 1 is a side elevation of a surge arrester constructed and arranged in accordance with this invention.

Fig. 2 is a horizontal section on an enlarged scale taken on line 2-2 of Fig. 1.

Fig. 3 is an enlarged, inverted plan view of the surge arrester illustrated in Fig. 1.

In the drawings, wherein is shown for purposes of illustration, merely, one embodiment of the invention, A designates generally an electrical protective device. The particular protective device illustrated in the drawings comprises an insulator l of the petticoat type at the upper end of which an upper terminal 2 is suitably fixed, said upper terminal being provided with a block portion 2' which is provided with an opening formed therethrough through which an end portion of a member 3 is extended. The member 3 is secured to the block portion 2' of the upper terminal 2 by a clamping bolt 4, and said member 3 is shaped as is shown to good advantage in Fig. 1; that is to say, said member 3 includes a substantially horizontal portion 3a, a downwardly curved portion 3b, and an upwardly inclined portion 30 which projects from said downwardly curved portion 3b.

The member 3 has associated therewith an arm 5 which is secured at its lower end to a supporting element 6 that is fixed to the insulator l through the instrumentality of a U-bolt 6. The

arm 5 is provided with a substantially vertical portion 5a and an upwardly and outwardly inclined portion 5b and said arm is secured to the supporting element by a bolt 1, said inclined portion of said arm being spaced from the portion 3b of the member 3 to provide a gap G therebetween. The supporting element 6 has fixed thereto an upper contact arm 8, and at its lower end the insulator I is provided with a ground terminal 3 to which is fixed a lower contact arm Ill.

The lower contact arm I0 is formed from a length of resilient wire, or rod material, which is so formed and shaped as to provide said lower contact arm with transversely spaced, spirally coiled portions ii, transversely spaced portions i2 being extended from the centers of the coiled portions II and being projected rearwardly and said portions i2 terminating in an upwardly extended loop l3 through which the shank of a bolt I4 is extended for securing the lower contact arm III to the ground terminal 9. The lower contact arm ill includes transversely spaced portions I5 which extend forwardly from the lower portions of the coiled portions ll thereof, forward sections of said portions l5 being arranged in closely related parallelism to provide the forward portion of the lower contact arm l0. At the forward end of the lower contact arm Hi the portions I 5 are bent rearwardly to provide opposed gripping portions i6, and these gripping portions are flared outwardly at their rear ends as is shown in Fig. 3, sleeves I1 and a cap l8 being employed to retain various parts of the forward portion of the lower contact arm ill in their proper related position.

The forward portion of the upper contact arm 8 is constructed in accordance with the forward portion of the lower contact arm ID as described above, and as shown in Fig. 3; that is to say, the wire or rod-like material of which said forward portion of said upper contact arm 8 is formed is shaped to provide said upper contact arm with opposed gripping portions l9 (one of which is shown in Fig. 1) and these opposed gripping portions l9 correspond with the gripping portions ii of the lower contact arm Ill. The upper contact arm 8 is provided with a 2i which retain parts of said upper contact arm in their proper related positions, and said upper contact arm includes a rear portion 22 which is secured to the supporting element 6 by the bolt 1 which serves also to secure the arm 5 to said supporting element.

The electrical protective device A includes a surge link structure 23, said surge link structure comprising a tube structure 24 from the opposite ends of which cables 25 are extended. The cables 25 are provided with tool-receiving eyes 25 at their outer ends, and said cables are arranged in electrical contact with conductive elements disposed in spaced relation within the tube structure 24 to provide a gap therein (not shown). When the protective device A is to have the surge link structure applied thereto the lower cable 25 of said surge link structure is drawn, with the aid of a suitable insulated tool, into one of the gripping portions of the lower contact arm ii. The surge link structure is then elevated with the aid of the tool and the upper cable 25 of the surge link cap 20 and a sleeve structure is drawn into one of the grippin portions is of the upper contact arm 8, and such elevation of the surge link structure elevates the outer portion of the lower contact arm It so as to tension the coiled portions i l of said lower contact arm and store up force therein which tends to swing the outer portion of the lower contact arm in a downward direction.

The ground terminal 9 of the protective device A is grounded and when, in-the use of said device A, a surge on the line protected by the device seeks a path to ground, it will form arcs across the air gap G (which normally keeps the line potential of! of the surge link structure 23) and across the gap within said surge link structure 22, and will pass to ground by way of the lower contact arm l and the ground terminal 8. A follow-up power are will be established across the gap within the tube structure oi the surge link and this follow-up power arc will be extinguished within said tube structure of the surge link. If, however, the surge link fails to properly extinguish the power arc, the continuance of the arc will destroy the surge link structure by burning the tube structure thereof so that'its opposite end portions are separated, and when this occurs the outer portion of the lower contact arm ill will swing downwardly, in response to force imparted by the tensioned, spirally coiled portions ll of said lower contact arm ll, to quickly jerk the surge link structure apart, and thereby free the protective device from ground by creating a substantial air gap which will prevent re-establishment of an arc.

Prior to the present invention, surges passing to ground in the operation of a protective device of the type designated herein by the reference character A, were required to follow the turns of the coiled portions I l of the lower contact arm ill of the protective device, and this produced an undesirable situation which in some cases, at least, interfered to some extent with the efliciency oi the protective device and reduced the life of the surge link 23. In other words, it has been found in some cases that very high current, high frequency surges induced by lightning will not follow the turns of said coiled portions II, and that the coiled portions offer considerable impedance to the current, thus causing a reflected wave which when imposed on the original wave resulted in a momentary current which had a tendency to burst the tubular portion of the surge link 22. This situation has been corrected in accordance with the present invention by providing a shunt structure which shunts the surges around the coiled portions I l of the lower contact 4 tions of the spaced portions 21 of the shunt element 28 is an elongated loop portion II which is interposed between and contacts at its oppomte sides with lower parts of the coiled portions ll of the lower contact arm It. It is to be noted that the loop portion 30 of the'shunt element 28 is slightly tapered from back to front and as a result said loop portion is wedged between the coiled portions ll of the lower contact arm It, and thus makes close electrical contact engagement with the parts of the coiled portions oi the lower contact arm with which the opposed side portions of said shunt element contact."

Because 01' the presence of the shunt element 28 in the structure of the protective device A, it is plain that a direct path for. surges is provided between the surge link 23 and the ground terminal 9 which causes the surges to by-pass the coiled portions I l of the lower contact arm ill and thus eliminate the diiiiculties heretofore encountered, as recited above, when the surges were required to follow the turns of said coiled portions. In addition to providing the shunt element 26, the protective device A may be provided with a shunt 3| between the portion 512 of the arm 5 and the upper contact arm 8, so as to provide a direct conductive path between these parts and eliminate the V-shaped conductive path which would be present in the absence of the shunt 2|.

I claim:

1. The combination of an electrical cutout provided with an outgoing terminal and a lower contact arm which is connected to said outgoing terminal and is provided with transversely spaced coiled portions for providing said lower contact arm with increased resiliency, and a shunt member connected to said outgoing terminal and having a portion which is disposed between said coiled portions of said lower contact arm in contact with parts thereof for providing a conductive path directly from said lower contact arm to said outgoing terminal which by-passes said coiled portions of said lower contact arm, the portion of said shunt member which is disposed between said coiled portions of said lower contact arm being in the form of a loop.

2. The combination of an electrical cutout provided with an outgoing terminal and a lower contact arm which is connected to said outgoing terminal and is provided with transversely spaced coiled portions for providing said lower contact arm with increased resiliency, and a shunt member connected to said outgoing terminal and having a portion which is disposed between said coiled portions of said lower contact arm in contact with parts thereof for providing a conductive arm In of the protective device, and thereby provides a direct path to ground for the surges.

The shunt structurereferred to comprises an element 26 which is formed from a single length of wire, or rod-like material, said element being provided with a pair of spaced, upwardly. extended end portions 21 which contact with a face of the ground terminal 9. These portions 21 of the shunt element 26 are secured to the ground terminal 9 by the bolt 14 previously referred to herein as serving to secure the lower contact arm It to said ground terminal, there being a washer 28 interposed between the spaced portions 21 of the shunt element 28 and the upwardly extended loop [3 of the lower contact arm, and a second washer 29 being interposed between the nut 9' of the bolt 9 and said loop ii of the lower contact arm. Extended forwardly from the lower porpath directly from said lower contact arm to said outgoing terminal which by-passes said coiled portions of said lower contact arm, the portion of said shunt member which is disposed between said coiled portions of said lower contact arm being in the form of a loop of tapered elongated shape.

3. The combination of an electrical cutout provided with an outgoing terminal and a lower contact arm which is connected to said outgoing terminal and is provided with transversely spaced coiled portions for providing said lower contact arm with increased resiliency, and a shunt member connected to said outgoing terminal and having a portion which is disposed between said coiled portions of said lower contact arm in contact with parts thereof for providing a conductive path directly from said lower contact arm to said 5 outgoing terminal which lay-passes said coiled CHARLES ADIN FOX.

6 REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 657,414 Hundhausen Sept. 4, 1900 1,746,650 Harrington Feb. 11, 1930 1,773,014 Seslar Aug. 12, 1930 2,272,370 Fox Feb. 10, 1942 

